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Discussion Starter · #1 ·
will a cx rotor fit a gl? i cannot find any rotors on ebay that are gl500 specific. i cross referenced part numbers on the dealer site and the part numbers are different but it won't say if the parts have any appreiciable difference.
 

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Why don't we start this with some pix and a drawing showing all the dimensions? I'd be glad to print something like that out to have with me the next time I hit a wrecker yard.
 

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Short answer, no. The CX single rotor is larger diameter. The mounting holes in the wheels for the rotor bolts and spacing dimensions are the same size.

A CX front wheel can have the CX rotor unbolted, removed and then install a pair of GL500 rotors, left and right on the wheel. You will then find that the wheel is now rotating backwards, when mounted to the GL500 forks to accept the GL500 speedometer gear case. No problem, just remove and remount the tire for desired rotation direction. Use the bolts and nuts removed from the GL500 wheel to mount the dual rotors, they are slightly longer in length and also take different wrench size compared to bolts off the CX500 wheel. (Is someone somewhere going to come forward and challenge the viability of rotating wheel bearings in the reverse direction after 30 years?)



I performed this operation yesterday (Monday) to replace a bent front wheel on a 1981 GL500, using a replacement wheel from a CX500 1979? parts bike. That is, except for the tire removal. Additional note, the wheel for the CX500 is labeled as a different size as the wheel for the GL500 which is slightly wider. Both are 19" though.



Neglected to take photos for some reason, too busy I suppose, although I do have some earlier photos that I sent to Admin on another CX500 GL500 board, that show the unmounted CX500 and GL500 wheels and rotors side by side, also the GL500 forks left and right. That was related to converting a CX500 to dual rotor and required the GL500 forks with left and right caliper mount holes, also the triple trees as the forks are larger diameter.
 

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If I'm not mistooken, as I all too often am, a rotor off a single caliper GL500 is the same as the the rotor off a single caliper CX500. I did some hunting last year for one on the 'bay and I seem to recall through conversations with various sellers that the dimensions were the same.
 

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Discussion Starter · #5 ·
i'm going to try turning my existing one. i need a caliper rebuild kit as well as new pads and i don't even know yet if this caliper is salvagable. the pistons are rusted in place in the bore. i'm soaking it now and will check it around lunch to see if i can get it apart for a rebuild. our brake lathe at work should be able to turn this but i don't know if theres enough material to make it usable. 6mm is the limit and i'm at like 6.2 now and some of these grooves are pretty deep. i'll post the results when i have them.
 

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Word is the rotors are made from stainles steel (or so the eBay guy claims) thus not turnable, they need to be surface machined.
 

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If I'm not mistooken, as I all too often am, a rotor off a single caliper GL500 is the same as the the rotor off a single caliper CX500. I did some hunting last year for one on the 'bay and I seem to recall through conversations with various sellers that the dimensions were the same.


Don't all GL bikes have dual rotors in the front?
 

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I suspect that the GL500 I was working on was an Interstate version. Has dual rotors on the front. Don't have a GL500 single rotor available to measure rotor diameter or check wheel size. I'll go write down the wheel sizes and post somewhere.

1.85 X 19 CX500 C

MT2.15 X 19 GL500 1981

Added 10/20/2010

The GL500I'81 Silver Wing Interstate was sold in 1981

The serial number began JH2PC021*BM000007.

Checked the serial # and This is what I was working on that was equipped with dual rotors
 

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Discussion Starter · #10 ·
mine has a single front rotor. i'm no longer worried about the front rotor because the caliper is completely f'd and the bike is having trouble reliably starting. my priorites on this project are written in pencil because they are constantly changing.
 

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I suspect that the GL500 I was working on was an Interstate version. Has dual rotors on the front. Don't have a GL500 single rotor available to measure rotor diameter or check wheel size. I'll go write down the wheel sizes and post somewhere.

1.85 X 19 CX500 C

MT2.15 X 19 GL500 1981

Added 10/20/2010

The GL500I'81 Silver Wing Interstate was sold in 1981

The serial number began JH2PC021*BM000007.

Checked the serial # and This is what I was working on that was equipped with dual rotors






My single rotor appears to measure about 5 and 1/4 inches from the center of the axle to the outside. I don't know how accurate you need that measurement to be.
 

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You can of course machine stainless steel, you just have to make sure you take them to a machinist using tipped tools and not carbide steel tools, which will overheat, and fail. Almost certainly the same type of place will have a surface grinder also. Old discs of this type are often quoted with overly generous minimum thickness figures, but I would not be too concerned about dipping a little under it
 

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Seems to me the price of a good used one from a low mileage bike might be more attractive pricewise.



I sure miss an old friend that finally fully retired and sold everything, he had a full auto shop so big he rented his own building to house it and of course allowed me free access. Already semi-retired after a great career in engineering, his hobby was restoring old cars and, being single, had no problem spending his money anywhere he darn well pleased so he had a lot of specialized equipment and tools.



Anymore I feel lucky to be able to tip the guys at the corner gas station just to use their lift on a Sunday. Can't do much of the work I used to (but also getting a bit old to do the heavy stuff anyway) yet it's nice to get under the car and give everything a good going over every now and then, most mechanics nowadays will "do what they have to" but won't take the time to really look stuff over for potential problems that could arise in future nor lubricate things you wouldn't see mentioned on a typical maintenance list.
 

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I have found that although interchangeable The rotors on the single disk models are 5mm thick... on the doubles they are 3.5mm. I replaced the single 30mm piston stock caliper from my 82cx with a 32mm piston caliper from a 84 700sc dual caliper. The rotor was interchangeable with a slight increase in surface contact area. After replacing the 28 year old line and replacing the stock MC. My front brake works as good as I'll need. I can either come to a fairly smooth stop, or (almost) endo the thing. Unless I gain weight or top speed, I'm going to stick with the single caliper.



So if you are going to change rotors, you may have to get calipers to match as a thinner rotor with thin used pads ain't going to last too long
 
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